Hydraulic motor mechanism



y 15, 5- c. R. SACCHINI ET AL 21,376,009

HYDRAULIC MOTOR MECHANISM Filed April '7, 1943 I 2 Sheets-Sheet lINVENTORS Cow/wa s IE5AccH/N/ LOAA/N M VANOERVOOPT ATTORNEY foroperating main navigational controls.

Patented May 15,1945

UNlTED STATES PATENT OFFICE HYDRAULIC. MOTOR LIECHANISM Columbus R.,Sacchini, Euclid, and Lorain N. Vandervoort, Cleveland, Ohio, assignorsto The Marquette Metal Products Company, Cleveland, Ohio, a corporationof Ohio Application April v, 1943, Serial No. 482,124

'7 Claims.

This invention relates to hydraulic motors and more particularly tohydraulic motors capable of producing alternate rotary motion of a powerdisclosed is described as applied to the most exacting of such uses,namely that of driving the windshield wiper blades on aircraft. Numerousmechanisms have been devised for actuating window and windshield wiperblades on aircraft by energy derived from-fluid pumps or other fluidpressure sources currently provided on such craft Such priorarrangements have not been as satisfactory as desired because of theirfailure completely to overcome all of the many problems and to meet theexacting requirements of installa tions of this character.

Among these numerous problems are those of fluid motor must be capableoi supplying adequate power to enable the wiper blades to clear thevision surface under adverse weather conditions unique in the operationof aircraft and under conditions presented by high velocity slip stream.Furthermore, it is essential that the fluid motor be manufactured-fromthe light nonmagnetic metals or alloys so as not to add to the non-payload of the aircraft or interfere with the magnetic navigationinstruments, and that provision be made for altering conveniently theextent of the sweep of the wiper blades.

The motion of the output shaft of many of the prior hydraulic motorsdesigned to drive the blades of airplane window and windshield wipershas been rectilinear or push-pull in nature and consequently it has beennecessary to provide motion converter units at the wiper blades tochange the push-pull motion into alternate ro-. tary motion. Thisadditional equipment with its associated shafting has resulted ininstallations which occupy too much space and are of undue complexity.In addition, prior fluid motors have been provided with reciprocatingslide valves which have numerous relatively sliding surfaces and areinherently complicated and therefore expensive and diflicult to maintainin serviceable condition.

An object of the present invention is to provide an improved hydraulicmotor.

A further general object is to provide a hydraulic motor which is ofsimple and rugged construction and comprised of a minimum number ofparts which are simply and quickly assembled and disassembled formanufacturing and servicing purposes.

Another object is to provide a hydraulic motor adapted to drive a windowor windshield wiper :blade or blades which motdr successfully meets' allof the foregoing requirements and in which the disadvantages of most ofthe prior structures are eliminated.

Other general objects are to provide a device of the above indicatedcharacter which (1) is easy to manufacture in that it has a minimum ofmoving parts and required accurate machining is reduced to a minimum,(2) may be constructed without the use of iron or steel, (3)incorporates a rotary valve mechanism of simplified design, (4) thenecessary fluid passages are easily provided,.(5) the output shaftispositively driven with alternate rotary motion, (6) has a housing ofsimplified design, and (7) the extent of wiper blade movement is readilyadjustable through a wide range in infinite steps.

A more specific object is to provide a hydraulic motor in which thepower output shaft is driven with an alternate rotary motion in responseto reciprocation of a piston controlled by a'rotary valve actuated by asnap action mechanism.

Another specific object is to provide a hydraulic motor in which theextent of oscillation of a power output shaft is adjusted by .varyingthe position of a pivot block with respect to the center of rotation ofa trip yoke controlling the valve element of the motor.

Yet another specific object is to provide a snap acting rotary valve fora hydraulic motor in which a trip yoke for the valve is rotatablysupported by the rotating valve element.

Another specific object is to provide improved fluid passage means in ahydraulic motor hous-. ing which permits controlled flow of theactuating fluid within the housing for lubricating purposes.

Other objects and advantages will become apparent from the followingspecification wherein reference is made to the accompanying drawings, inwhich:

Fig. 1 is a side elevation of the hydraulic motor of this inventionshown in association with a typical windshield panel structure (lattershown in section) and arranged to drive a windshield wiperblade-supporting arm; Fig. 2 is a vertical sectional view takengenerally on the line 22 of Fig. 1; Fig. 3 is a vertical sectionalviewtaken generally on the line 3-3 of Fig. 2; Fig. 4 is a verticalsectional view taken generally on the line 4-4 of Fig. 3; Fig. 5 is apartial horizontal sectional view taken generally, on the line 5-5 ofFig. 4; Fig. 6 is a partial vertical sectional view taken generally onthe line 66 of Fig. 1; and Fig. 7 is a fragmentaryyiew showing a detailof the yoke assembly.

In Fig. 1 the hydraulic motor M 01 this invention is shown mounted atthe top of a representative airplane windshield panel A with itsoscillatable power output shaft I extending through framework B of thepanel to actuate a wiper blade mechanim 2 secured on the outer end ofthe shaft I so as to be driven thereby to efiect oscillation of a wiper'blade 3. The motor M may be fastened in position by means of a hex nut4 threaded on the end of a bushing 5' which extends from the motorthrough the framework B and supports the shaft I.

Fluid under high pressure from a suitable source (not shown) is suppliedto the motor M through a high pressure conduit 6 attached to the motorby means of a suitable tube coupling I, and low pressure exhaust fluidis carried away from the motor through a low pressure conduit 8 attachedto the motor by means of a suitable tube coupling 9.

Although the hydraulic motor 8 is illustrated as driving but a singlewiper blade 3, additional wiper blades could be operated from a singlemotor through the use of appropriate motion transmitting mechanism in awell known manner.

The motor occupies but little more space than Y present electricallydriven,speed reducing motion converter units, and, since an electricmotor is not utilized, considerably less space is required for thecomplete windshield wiper blade driving mechanism. As shown, in Fig. 1,the use of the motor of this invention eliminates the need for auxiliarymotion converter units such as are associated with the push-pull outputshafting of the prior types of fluid motors, and it is apparent that themotor can be readily installed in any airplane with a minimum ofinterference and trouble.

Referring tothe construction of the hydraulic motor M, a housing for themotor comprises a substantially cubical, hollow main body member IDhaving an integral side wall I I (Figs. 2 and 4) and an opposite openside closed by a cup-shaped head body member I2 having a centralsocketed portion l3 secured in position by suitable means such as capscrews I4 passing through openings in an integral, flange portion [5.The screws are received in complementary threaded sockets in cornerportions of the walls of the body iii. A butt type joint between theflange I5 and the body I0 is suitably sealed against fluid leakage as bya compressible gasket l6, and (e. g. for aircraft use) the cap screws I4may be secured against becoming loosened as by a suitable tie wire I8passing through openings in respective heads of the screws I-l.

Ihe body Iii has a cup-shaped extension is projecting from the side wallll opposite the head body member I2, a hollow, generally cylindrical,extension 20 projecting from arear wall 2|, and a tubular extension 22projecting from a front wall 25. The body members ill and i2 arepreferably cast from a suitable light, nonmagnetic metal or alloy. Whenthe body members I8 and I2 are in assembled position, the cup-shapedportions l3 and I9 of the respective body members are aligned atopposite sides of the motor M and define piston chambers 25 and 26,respectively, within which a double-ended piston 28 is adapted toreciprocate.

In addition to the piston 28, the operating mechanism of the motor Mcomprises, as indicated on Fig. 3, a rotary valve assembly 29, an outputshaft driving rack and pinion assembly 38, a yoke assembly 3|, and asnap action mechanism 32, all contained generally within the body I0.

As will be described more in detail hereinafter, the rotary valveassembly 29 is operableto direct fluid under high pressure from the highpressure inlet conduit 6 through suitable passages drilled or otherwisesuitably formed in the walls of the body I0 and the head I2 alternatelyto the piston chambers 25 and 28 thereby to eifect reciprocation of thepiston 28. The piston, as a result of such reciprocation, drives thepower output shaft I of the output shaft assembly 30 with an alternaterotary motion and operates the yoke assembly 3I which cooperates withthe snap action mechanism 32 to effect properly timed operation of therotary valve assembly 29. Exhaust fluid from the piston chambers 25 and28 passes into the low pressure outlet conduit 8 under the control ofthe valve assembly 28 after the exhaust fluid has passed through theinterior of the body 10 where it serves adequately to lubricate all ofthe moving parts, thus obviating the necessity for other speciallubricating means.

As shown in Figs. 3, 4 and 5, the rotary valve assembly 29 is containedwithin an opening 33 which extends through the rear extension 20 of thebody I8 into the interior of said body and comprises a flanged bushing34, a cylindrical valve plug or gate element 35 rotatably supported bythe bushing 34 in close fitting relation thereto, and an annular valvegate and bushing retainer and pressure outlet member 38. Said member 38is in the form of a threaded sleeve which serves to support the outletconduit 8 through the intermediary of a threaded coupling 9 screwedcentrally into the member 38. The bushing 34 is pressed into the opening33 with its flange 40 axially abutting an annular shoulder 4| defined bya threaded counterbore portion 42 of the opening 3 3. The bushing 34 hasfour ports 44, 45, 48 and 41 which, as shown in Fig. 4, are spacedequally about the periphery of the bushing.

The inner top end portion of the bushing 34 is cut away as at 48 (Fig.3) to permit and limit oscillation of an integral bifurcated arm 36 ofthe valve gate 35 which is oscillatably driven through an arc ofapproximately sixty degrees by operative engagement of the arm 36 withthe snap-action mechanism 32 as described later herein.

A central axial bore BEIthrough the gate 35 is counterbored at its innerend to enable the gate rotatably to receive and support a bearing pin 5|integral with a slotted trip yoke 52 which is part of the yoke assembly8i, and is counterbored at its outer and to define a chamber 54communicating with the central opening in the retainer'sleeve member atwhich, through the fitting ii, supports and communicates with theexhaust or outlet conduit 8. Diametrically opposed parallel tangentialgrooves in the gate 35. in the common plane of the ports 34, d5 46 andIll, terminate at chordal groove-bottom portions outer face and isscrewed into the counterboredportion 42 of the opening 33 with its innerface operatively abutting the outer face portions of the bushing 34 andthe valve gate 35. It is thus seen that the plug 38 absorbs the endthrust of the valve gate 35. The threaded joint between the sleeve 38and the extension 28 may be sealed with a suitable plastic sealingcompound during assembly.

When in the turned position illustrated in the drawings (Fig. 4) thevalve gate 35 permits fluid to flow from the high pressure inlet conduit6 (see Figs. 1 and 6) through a pipe threaded opening 88 in the wall 2|,which opening receives the tube coupling 1, into a passage 6| and thencethrough the port 45 into the valve chamber 55. From the valve chamber 55the high pressure fluid flows through the port 44 (Figs. 4 and andpassages 62, 62', 63, 64 and 65 to the outer end of the piston chamber25. Concurrently, exhaust fluid is permitted to flow from the outer endof the piston chamber 26 through passages 88, 69, I8 and II and the port48 into the valve chamber 58. As a result, the piston 28 is moved fromleft toright as viewed in Fig. 4. From the valve chamber 56 .the exhaustfluid flows through the port 8'! and the passages I2 and "into theinterior of the body I8 where it serves to lubricate the moving parts.Displaced fluid flows from the interior of the body I8 through an axialbore 5I in the bearing pin 5i of the trip yoke 52 and the central bore58 in the valve gate 35, aligned therewith, into the chamber 54 andthence through the low pressure outlet conduit 8.

When the valve gate 35 is turned to a position displaced approximatelysixty degrees from the position shown in the drawings (new position ofarm 38 indicated by dot and dash lines in Fig. 4 only) the fluid underhigh pressure from the inlet conduit 6 is directed by the valve assembly29 into the outer end of the piston chamber 26 and the fluid ispermitted to exhaust from the piston chamber 25. Consequently, thepiston 28 then moves from right to left as viewed in Fig. 4 andcompletes a single cycle of operation.

Describing the internal fluid passages more in I detail, the passage 5i(Fig. 3) is defined by a The outer ends of the passages 6i and I3 aresealed by suitable plugs I4 and15, respectively, which may be screwthreaded or pressed into the outer ends of the respective passages.

The passage 82 (Figs 4 and 5) is defined by a lateral bore in the endwall 2| and is aligned with a bore in the flange l5 defining the passage82' which intersects at its end'a horizontal bore defining the passage63. The passage 63 intersects at its inner end (Fig. 5) an axial bore ina thickened portion I6 of the cup-shaped portion I3 defining the passage64. The outer ends of the passages 53 and 64 are sealed by plugs 11 andI8, respectively. A bore extending obliquely across the end of thecup-shaped head body portion I3 (direction indicated by the line 5-'-6on Fig. 1) intersects a reduced end portion 18 of comprises opposedpiston heads 86 and 81 couthe piston chamber 25 and extends to thepossage 64 near the plug- 18 and defines the passage 65 (Figs. 5 and 6)which is sealed at its outer end by a plug 88.

The passage II with which th port 46 is aligned is an extension beyondthe opening 33 of the lateral bore in the end wall 2| which defines thepassage 62 and intersects a horizontal bore in the side wall I I whichdefine the passage I8. The passage 18 intersects at its inner end anaxial bore in a thickened portion 8| of the cupshaped extension I9defining the passage 59. The passages 69 and18 are sealed at their outerends by plugs 82 and 83, respectively. A bore extending obliquely acrossthe end of the cup-shaped extension I9 intersects a reduced end portion84 of the piston chamber 26 and extends to the passage 88 near the plug83 and defines the passage 68 sealed at its outer end by a plug (Fig.6).

The piston 28, shown most clearly in Fig. 2,

pled by a rack portion 89 of generally rectangular section havingsuitable teeth 98 cut in the top of a central portion of reduced width.The piston heads 86 and 81 are reciprocally supported in tubular linings9I and 92, respectively, pressed into the piston chamber 25 and 26,respectively, v

and extending therefrom a short distance into the cubical chamberdeflned'by the body I8. Each of the piston heads 86 and 81 has asuitable cupshaped elastic sealing member 94 secured to the outer endface thereof as by a screw 95.

The piston 28 cooperates with the output shaft assembly 38 to drive thepower output shaft I 'with an alternate rotary motion by virtue of theteeth 98 of the rack portion 89 meshing with a gear 96 suitably securedto a squared inner end 98 of the power output shaft I against a flange99 (Fig. 3) integral with the shaft. The flange 99 serves to space thegear 96 from the inner end of the bushing 5 and absorbs outward axialthrust of the shaft I which is rotatably supported bi the bushing 5. Thebushing 5 is pressed into a central opening i8I in the short extensionor pad 22 and is further secured in position by cap screws I82, only oneof which is shown in Fig. 1, passing through openings in the flange I84on opposite sides of the shank portion of the bushing 5 and receivedwithin threaded sockets in the pad 22. The outer face of the extension22 is cham'fered at thecentral opening Illl to pro- I88 and passingthrough an opening in a widened 'portion (-see Fig. 5)- of the rackportion 89 of the piston 28. The widened portion of the rack has agroove H6 which receives the tongue 4 and thus the support I88 becomesin effect an integral part of thepiston 28 and moves transverselytherewith.

A widened face portion of the support I88 opposite from thestud II2 hasan elongated slot H8 in which the pivot block I89 is slidably mounted.The pivot block I89 is held in adjusted position within the slot II8 byvirtue of its threaded engagement with the adjusting a head at its lowerend. By turning the screw IIO as by means of a screw driver received ina slot H9 at the top of the screw IIO the pivot block I09 can be raisedor lowered to adjust in infinite steps the angular travel of the outputshaft I in a manner to be described. A suitable lock nut I20 is providedat the top of the screw 0 to lock the screw in adjusted position, andaccess to the screw 0 and the nut I20 is enabled by removing a plug I2Ithreaded into an opening in the top wall of the body I0 directly abovethe screw 0 and provided with an annular sealing gasket I22.

A groove I24 in the face of the trip yoke 52 opposite the bearing pinextends from the bottom substantially to the top of the yoke 52and'slidably receives a driving pin I25 integral with the pivot blockI09,'a bearing block I28 being interposed between the pin I25 and thegroove I24 to minimize wear on the pin and groove. As can be seen mostclearly in Figs. 3 and 4, rectilinear reciprocation of the piston 28causes similar movement of the pivot block support I 08 and the pivotblock I09. As a result of this movement the driving pin I25 slides inthe groove I24 and oscillates the yoke 52 about the center of thebearing pin 5| which is rotatably received in the inner counterboredportion of the opening 50 in the valve member 35 as previouslydescribed. The extent of oscillation of the yoke 52 with respect to thereciprocated position of the piston 28 is determined by the adjustedposition of the pivot block I09 with respect to the axis of the bearingpin 5|.

An arm I28 extending outwardly from the top of the trip yoke 52 in thedirection of and parallel to the bearing pin 5| has a circular openingI28 therethrough which is chamfered at the lower face portion of the armI28 to provide a seat for a hemi-spherical head I29 of a spring perch orretainer I30 which forms a part of the snap action mechanism 32. Thehead I29 extends part way into the opening I28 and has an upwardlyextending pin portion I3I which serves to prevent the possibility ofdisengagement of the retainer I30 from the yoke 52.

A downwardly extending cylindrical shaft portion I32 of the springretainer I30 isslidably received in a longitudinal bore of a trunnionblock I34 which comprises a lower bar portion I35, an intermediateenlarged portion I38, and an upper reduced cylindrical portion I3I. Apair of opposed bearing pin portions I38 (only one of which is shownFig. 4) extending outwardly from the. lower end of the bar portion I35are substantially semi-circular in cross section and are received inrespective complementary openings I38 in the legs of the bifurcated arm38 of the valve member 35. Slots I40 open respectively into the openingsI39 so that the pin portions I38 may be readily inserted into theopenings I39 in one relatively turned position of the bifurcated armsand pins.

A coiled compression spring I42 surrounds the portion I3I of thetrunnion I34 and bears against an annular shoulder defined by theportion I31 and the shoulder I38. The upper end of the spring I42 bearsagainst a similar annular shoulder formed adjacent a lower reducedcylindrical portion I44 of the spring retainer I30.

A more comple e understanding of the construction and cooperation of thevarious parts of the motor M may be had 'from the following descriptionof operation. As stated previously:

with the valve gate 35 in the turned position shown in the drawings,fluid under high pressure flows from the high pressure inlet conduit 8through the passage 8|, the port 45, the valve chamber 55, the port 44,and the passages 82 to 85, inclusive, into the piston chamber 25 andforces the piston 28 toward the right, as viewed in Fig. 4, left Fig.2-the piston 28, however, being shown at the center of its path oftravel. Concurrently, exhaust fluid flows from the piston chamber 28through the passages 68 to II, inclusive, the port 48, the valve chamber58. the port 41, the passages I2 and I3, the interior of the body I0,the bores 5| and 50, and the chamber 54 into the low pressure outletconduit 8. It should be noted (Fig. 3) that the end of the bore 5| whichopens into the groove I24 is enlarged to provide a passage around thebearing block I28 when the pivot block I 09 is g in the lowermostadjusted position.

Due to the operative engagement between the teeth of the rack portion 89with the gear 98, this translatory movement of the piston 28 causespartial rotation of the shaft I and consequent wiping action of thewiper blade 3. Concurrently, and by virtue of the same translatorymovement of the piston 28, the pivot block support I08 together with thepivot block I09 move to eflect, due to operative engagement between thepin I25 and the slot I24, movement of the top of the trip yoke 52 (tothe right, Fig. 4) in an arc the center of which is the axis of thebearing pin 5|. Movement of the yoke 52 to the right compresses thespring I42 as the spring retainer I30 moves due to the cooperationbetween the head I29 and the opening I28 in the arm I28. Movement of thespring retainer I30 is about the trunnion pins I38 which turn in theopenings'l39. The yoke 52 moves until the snap action mechanism 32 is inits dead center position, and slight additional movement of the arm I28permits the spring I42 to expand and drive the arm 49 and the valve gate35 through an arc of substantially 60 to the position shown by dot anddash lines in Fig. 4.

Movement of the valve gate 35 into the 60 turned position permits highpressure fluid to flow through the passage 8I, the port 45, the valvechamber 58, the port 48, and the passages II, I0, 89 and 88 into thepiston chamber 28 to arrest and reverse the mo ement of the piston 28.Concurrently fluid flows from the piston chamber 25 through the passages85, 84, 83, 82' and 82, the port 44, the valve chamber 55, the port 41,the passages I2 and I3, the interior of the body II), the bores 5I' and50,-and the chamber 54 into the outlet conduit 8. Reverse movement ofthe piston 28 causes reverse movement of the pivot block support I08,pivot block I09, and yoke 52 and consequently the snap action mechanism32 moves again through a dead center position beyond which the springI42 turns the valve gate 35 to its initial position.

It is thus seen that the piston 28 is reciprocated as long as highpressure fluid is supplied to the conduit 8 and effects alternate rotarymotion of the power output shaft I to effect wiping action of the blade3.

The extent of movement of the piston 28 and consequently the sweep ofthe wiper blade 3 is determined by the adjusted position of the pivotblock I09 which determines the amount of movement of the piston 28before the snap action mechanism 32 is eflective to turn the valve Bate35. As shown, the angular travel of the shaft I and the wiper blade 3can be adjusted, by turning of the screw ill] to raise and lower thepivot block I09, through a range from a minimum of 40 to a maximum of150, the adjustment being in infinite steps. by difierent proportioningof the parts, if desired.

We claim:

1. In a hydraulic motor having a power output shaft oscillatably drivenby a piston reciprocating in a piston chamber in response to alternatingmovement of a single rotary valve gate member controlling the supply offluid to said chamber, the combination including a swingable yokemechanism driven by said piston and a snap action mechanism operativelyinterposed between said yoke mechanism and said valve gate member, a.

positive connection between said snap action mechanism and said valvegate mechanism operable upon movement of said piston beyond apredetermined position in either direction of movement positively t movesaid valve gate member rapidly from one extreme position to anotherextreme position with a snap action to control thereby the flow of fluidto said piston chamber and reverse periodically the direction ofmovement of said piston, and means enabling adjustment of saidpredetermined position without requiring disassembly of any of thecooperating parts of the snap action mechanism.

2. In a hydraulic motor having a power output shaft oscillatably drivenwith alternate rotary motion by a double ended piston reciprocating inopposed piston chambers in response to alternate operation of a rotaryvalve controlling the supply of fluid to and from said chambersselectively. a yoke mechanism including a rigid arm pivoted on therotational axis of the valve and a spring toggle snap action mechanismconnecting said yoke arm to the valve and including a rigid toggle armsecured to the rotary valve for turning movement only therewith and aspring toggle arm connecting the rigid toggle arm to the yoke armwhereby said mechanisms are operable upon movement of said piston beyondpredetermined positions in opposite directions, respectively, to operatesaid valve mechanism from one position to another position with a snapaction to change thereby the flow-f fluid from one of said chambers tothe other of said chambers and a spring encircling said spring togglearm to operate said valve mechanism as the toggle passes dead center.

3. A hydraulic motor comprising a power output shaft, a pinion securedto said shaft, a double ended piston reciprocating in opposed pistonchambers in response to alternate operation of'a rotary valvecontrolling the supply offluid to and from said chambers selectively,said piston having a rack portion operatively in mesh with said pinion,whereby said shaft is oscillated by reciprocation of said piston, aswingable yoke mechanism driven by said piston, means within said yokemechanism for varying the effective operating length thereof, a snapaction mechanism operatively interposed between said yoke mechanism andsaid valve member and operable upon movement of said piston beyond apredetermined position to operate said valve mechanism rapidly from oneposition of rest to another position of rest with a snap action tochange thereby the flow of fluid from one of said chambers to theotherof said chambers.

A wider range can be obtained grooved or slotted trip yokerotatably-supported. 35 at one end by said valve member, a pivot block4. A hydraulic motor .as in claim 3 characterized in that said snapaction mechanism comprises a toggle mechanism one end of which is-rotatably supported in a lever arm integral with said rotary valve andthe other end of which terminates in a hemi-spheric'al section, and inthat said yoke mechanism is provided with an arm having a circularopening cooperating with said hemi-spherical section.

m 5. In a fluid pressure motor having a reciprocating piston withopposed piston heads slidable in piston chambers respectively, inresponse to alternate operation of a valve gate controlling the supplyof fluid to said chambers, a support attached to said piston, alongitudinally grooved tary motion of said yoke upon reciprocation ofsaid piston, and a snap action mechanism operatively interposed betweensaid yoke member and said valve gate to move said valve gate alternatelyfrom one position to another position with a snap 25 action consequentupon alternate rotary motion of said yoke.

6. In a fluid pressure motor having a reciproeating piston with opposedpiston heads .slidable in piston chambers respectively in response to30. alternate operation of a valve' member controlling the supply offluid to said chambers, an elongated support member attached to saidpiston and having an adjusting screw, a longitudinally 40 of said tripyoke upon reciprocation of said piston,

said valve member having two positions of movement, and a snap actionmechanism interposed between said trip yoke and said valve member tomove said valve member from one position to the other position with asnap action upon alternate.

rotary motion of said trip yoke.

7. In a fluid pressure motor, a reciprocating piston member havingopposed piston heads slidable in piston chambers respectively inresponse to alternate operation of a rotary valve. gate controlling thesupply of fluid to said chambers, a

guide member attached to said piston and with a guide surface extendingtransverse to the main longitudinal axis of the piston member, a slotted5;, trip yoke rotatably supported at one end 00- axially with said valvegate member, a pivot block movablyassociated with said yoke member onsaid guide surface and operatively engaging the slot of the trip yoke tocause alternate rotary motion of said trip yoke upon reciprocation ofthe piston member, means connecting the pivot block and guide member andturnable to adjust the block along said guide surface, said valve gatehaving two valving positions and a snap action mechanism interposedbetween said trip yoke and said valve gate to move said valve gate fromone valving position to the other position with a snap action uponalternate rotary motion of said trip yoke.

COLUMBUS R. SACCHINI. LORAIN N. VANDERVOORT.

